2018 Systems Engineering Written examination · Reading time: 9.00 am to 9.15 am (15 minutes)...

transcript

SYSTEMS ENGINEERINGWritten examination

Monday 19 November 2018 Reading time: 9.00 am to 9.15 am (15 minutes) Writing time: 9.15 am to 10.45 am (1 hour 30 minutes)

QUESTION AND ANSWER BOOK

Structure of bookSection Number of

questionsNumber of questions

to be answeredNumber of

A 20 20 20B 9 9 80

Total 100

• Studentsarepermittedtobringintotheexaminationroom:pens,pencils,highlighters,erasers,sharpeners,rulersandonescientificcalculator.

• StudentsareNOTpermittedtobringintotheexaminationroom:blanksheetsofpaperand/orcorrectionfluid/tape.

Materials supplied• Questionandanswerbookof24pages• Detachableinsertofmiscellaneousformulasinthecentrefold• Answersheetformultiple-choicequestions

Instructions• Writeyourstudent numberinthespaceprovidedaboveonthispage.• Checkthatyournameandstudent numberasprintedonyouranswersheetformultiple-choice

questionsarecorrect,andsignyournameinthespaceprovidedtoverifythis.• Unlessotherwiseindicated,thediagramsinthisbookarenotdrawntoscale.• AllwrittenresponsesmustbeinEnglish.

At the end of the examination• Placetheanswersheetformultiple-choicequestionsinsidethefrontcoverofthisbook.• Youmaykeepthedetachedinsert.

Students are NOT permitted to bring mobile phones and/or any other unauthorised electronic devices into the examination room.

©VICTORIANCURRICULUMANDASSESSMENTAUTHORITY2018

SUPERVISOR TO ATTACH PROCESSING LABEL HEREVictorian Certificate of Education 2018

STUDENT NUMBER

Letter

2018 SYSENG EXAM 2

SECTION A – continued

Question 1The term ‘torque’ refers toA. a type of force.B. the power generated by a motor.C. the amount of twist on an object.D. the amount of energy produced by a motor.

Question 2Gears are used for a range of reasons, including to change the direction of rotation and to increase torque or speed in various machines. In most cases, the driven gear can become the driver gear when a machine is slowing down.In which of the following gear sets can the driven gear not become the driver gear?A. crown wheel and pinion gearB. worm and wheel gearC. rack and pinion gearD. internal gears

Question 3Under the Occupational Health and Safety Act 2004, who is authorised to operate a piece of equipment with a ‘defective’ tag on it?A. any person designated or instructed by the employer to do soB. any person who has been trained to operate the machineC. anyonewhohasa‘testandtag’certificateD. no-one but the repairer

Question 4Which one of the following statements about energy is true?A. Energy can be created.B. Energy can be transformed. C. Potential energy can be destroyed.D. Kinetic energy can be easily stored.

SECTION A – Multiple-choice questions

Instructions for Section AAnswer all questions in pencil on the answer sheet provided for multiple-choice questions.Choose the response that is correct or that best answers the question.A correct answer scores 1; an incorrect answer scores 0.Marks will not be deducted for incorrect answers.No marks will be given if more than one answer is completed for any question.Unless otherwise indicated, the diagrams in this book are not drawn to scale.

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SECTION A – continuedTURN OVER

Question 5

Inthediagramshownabove,theforceFrequiredtokeeptheweightinplaceisA. 60NB. 30NC. 20ND. 15N

Question 6A300mmdiametercarwheelhasatorqueof200Nm.Whatisthedrivingforceofthewheelontheroadsurface?A. 30NB. 60NC. 30kND. 60kN

Question 7Ifamotorproduces12000Jofenergyinfourminutes,thepowerofthemotorwouldbeA. 48kWB. 3000WC. 500WD. 50W

2018SYSENGEXAM 4

Question 8

driver pulley100 mm

driven pulley

200 mm 400 mm 200 mm

ThepulleyratioofthesystemshownaboveisA. 1:8B. 1:4C. 1:2D. 1:1

Question 9Thethreadpitchofaboltis2mm.Theboltistightened90°afterfirstcontactwiththepartstobefastened.Howmuchstretchhasbeenappliedtotheboltshank?A. 0mmB. 0.25mmC. 0.5mmD. 1mm

Question 10Thenumber314159writteninengineeringnotationandcorrecttofoursignificantfiguresisA. 3.141×105

B. 3.142×105

C. 314.1×103

D. 314.2×103

Question 11Theterm‘watt’referstotheA. rateofdoingwork.B. sizeofsmallengines.C. amountofenergyusedinsteamengines.D. amountofenergyusedinelectricaldevices.

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Question 12

V12 VR1

Thevoltagedisplayedonthevoltmetershownaboveis12V.Whichoneofthefollowingoptionsismostlikelycorrect?A. R1isshorted.B. R2isshorted.C. R2isopencircuit.D. R3orR4isopencircuit.

Question 13Thefour-bandcolourcodefora1MΩ5%resistorisA. brown,blue,black,gold.B. brown,black,blue,gold.C. brown,black,green,gold.D. brown,black,black,yellow.

Question 14ThefunctionofaZenerdiodeinacircuitistoA. provideavoltagereference.B. rectifyanACvoltage.C. detectlight.D. emitlight.

2018SYSENGEXAM 6

Question 15

200 nF

ThetotalcapacitanceofthecircuitshownaboveisA. 0.5nFB. 181nFC. 202nFD. 2200nF

Question 16

0voltage (V)

time (ms)2 4 6 8

ThewaveformshowninthediagramabovecanbedescribedasA. digital.B. asinewave.C. adirectcurrent.D. analternatingcurrent.

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Question 17

Position W

Position Y

Position X

Position Z

Anammeterisusedtomeasurethecurrentfromthebatterysupplyingtheentirecircuitshownabove.Inwhichpositionshouldtheammeterbeplaced?A. PositionWB. PositionXC. PositionYD. PositionZ

Question 18Ahydrogencell,orfuelcell,worksbyA. burninghydrogenandoxygentogethertoproducewaterandelectricity.B. combininghydrogenandoxygenwithamembranecatalysttoproducewaterandelectricity.C. convertingwatertohydrogenandoxygen,andthenburningtheoxygentoproduceelectricity.D. convertingwatertohydrogenandoxygen,andthenburningthehydrogentoproduceelectricity.

Question 19BiofuelisbestdescribedasenergyproducedfromA. ahydrogencell.B. burningcoal.C. plantmatter.D. crudeoil.

2018SYSENGEXAM 8

END OF SECTION A

Question 20

20 Ω30 Ω12 V

ThetotalcurrentinthecircuitshownaboveisA. 600mAB. 400mAC. 200mAD. 133mA

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SECTION B – continuedTURN OVER

Emma is constructing a new house as shown in Figure 1 and she wants it to operate independently of any inputs, apart from those in the immediate environment. This type of house is known as an autonomous house.

Figure 1

Question 1 (5 marks)a. Apart from electrical solar panels to generate electricity, give two ways in which energy could

be harnessed from the sun for this autonomous house. 2 marks

b. How will heat energy be stored in this autonomous house? 1 mark

c. Identify two environmental considerations that should be taken into account when designing any engineering system. 2 marks

SECTION B

Instructions for Section BAnswer all questions in the spaces provided.All calculations must show appropriate formulas and working.Unless otherwise indicated, the diagrams in this book are not drawn to scale.

2018SYSENGEXAM 10

SECTION B – Question 2 –continued

Question 2 (14marks)Thehouseneedsasupplyofwater.Emmahasawatertank,butthewaterneedstobepumpedfromthetanktobeabletouseit.Emma’sinitialideaistouseahandpump,asshowninFigure2.

piston rod

Valve 1

Valve 2

handle

water outlet

piston

cylinder

Figure 2

a. Usingtheoptionsprovidedbelow,identifythepartslabelledAandBinFigure2. 2marks

effort fulcrum load

b. Namethetypeofmotionthehandpump’spistonusesinitsoperation. 1mark

c. Nametheclassofleverusedtooperatethehandpump. 1mark

d. Explainhowthehandpumpoperates.RefertothecomponentsValve1,Valve2,cylinderandpistonrodinyourresponse. 3marks

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piston rod

Valve 1

Valve 2

handle

water outlet

piston

cylinder

end of handle

900 mm

150 mm

Figure 3

e. WithreferencetoFigure3,calculatethemechanicaladvantageofthehandle.Showyourworking. 2marks

f. Ifthepistonmoves100mm,calculatetheapproximatedistancethattheendofthehandlewillmove.Showyourworking. 2marks

g. Calculatethepressureappliedtothewaterifanupwardforceof10Nisappliedattheendoftheleverandthecylinder’sdiameteris50mm.Showyourworking. 3marks

Nm–2

2018SYSENGEXAM 12

Question 3 (9marks)Emmafoundthattheflowofwaterfromthepumpwasnotconstant,soshedecidedtouseapumpthatoperatesonbothstrokesofthepiston.Figure4showsthepumpwithoutvalves.

connecting rod

piston

outlet

cylinder

Valve 1 Valve 2

Valve 4 Valve 3

Figure 4

a. OnFigure4,correctlydrawthefourvalves,whereindicatedbythelabelsValve1,Valve2,Valve3andValve4,thatwillletthewaterflowfromtheinlettotheoutletoneachstroke. 2marks

b. Inthetablebelow,givethestateofeachvalve(openorclosed)asthepistonismovingup. 2marks

Direction of piston Valve 1 Valve 2 Valve 3 Valve 4

movingup

c. Calculatethevolumeofwaterthatgoesthroughthepumpinoneminuteifthepistonhasadiameterof50mm,thestrokeofthepistonis50mmandthepumprunsat40strokesperminute.Showyourworking. 2marks

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d. Calculatethepressureinthecylinderiftheforceofthedownwardstrokeonthepistonis 50N.Showyourworking. 3marks

2018 SYSENG EXAM 14

SECTION B – continued

Question 4 (5 marks)Emma considers using a windmill to drive the water pump.

On the diagrams provided below, design a mechanism to convert four rotations of motion from the blades of the windmill to one cycle of the piston connecting rod moving up and down. Clearly label all components and dimensions.

windmill’sgearbox

20-teeth gear driven bywindmill’s blades

drive shaft from windmill’s blades

piston connecting rod

outlet

piston rod guide

water pump

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Question 5 (6 marks)Emma decides to make the windmill and water pump system herself.The table below lists the stages of the Systems Engineering Process.

Letter Stage of the Systems Engineering Process

A Test and diagnose/analyse performance.

B Design and model the system.

C Re-evaluate, modify and document.

D Evaluate and report on system produced and processes used.

E Research feasibility and alternatives.

F Plan, build and fabricate/integrate subsystems.

G Identify and document problem/need/opportunity/situation.

Select the most appropriate stage of the Systems Engineering Process for each task given below and write the appropriate letter for that stage next to the task. Only one stage per task is allowed.

Task Letter for stage

Find out the volume of water and the height that the water needs to be raised.

Cost a windmill and water pump.

Trial the operation of the water pump.

Generate a parts list and formulate a timeline.

Test the operation of the windmill and water pump.

Assess the final operation of the windmill against the design criteria.

2018 SYSENG EXAM 16

SECTION B – Question 6 – continued

Question 6 (16 marks)Emma decides to use low-voltage DC to provide power to her house. In making her decision, Emma explores the implications of using a 12 V rail or a 24 V rail. One factor in her decision is the resistance of the wire used. Different areas of the house have separate circuits. Emma decides to put all of the 10 living room lights on one circuit. Emma investigates using a 12 V supply and 12 V light globes. When all of the living room lights are on, the circuit draws 20 A. Emma initially considers using wire rated with a maximum constant current flow of 20 A and a resistance of 0.005 Ω/m.

a. Give two variables that affect the resistance of a wire. 2 marks

b. If the resistance of the living room wire is 0.15 Ω, calculate the length of wire used for the living room circuit. 1 mark

c. What is the voltage drop across the wire when all of the living room lights are turned on? Show your working. 2 marks

d. Calculate the voltage drop across the light globes when all of the living room lights are turned on. 1 mark

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SECTION B – Question 6 – continuedTURN OVER

e. Emma performed an experiment to check her calculations. She connected a 12 V light globe and a 12 V supply using wire with a resistance of 0.15 Ω in a circuit. This resulted in a voltage drop of 11.85 V across the light globe and a current of 1 A through the circuit.

Why is this voltage drop different from your answer in part d.? Use calculations to justify your response. 3 marks

2018 SYSENG EXAM 18

to power supplyand switch

Figure 5

f. Emma considers using a 24 V supply. She connects pairs of the 12 V light globes in the living room in series, as shown in Figure 5.

Assuming the rest of the wiring from the power supply to the switch is the same, calculate

i. the current through the new circuit 1 mark

ii. the voltage across each light globe. Show your working. 2 marks

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g. Calculate the efficiency of a circuit that has a 12 V supply and 11.85 V across the load. Show your working. 2 marks

h. Calculate the total power used by the 12 V circuit. Show your working. 2 marks

2018 SYSENG EXAM 20

Question 7 (7 marks)Emma wants to install a hall light that can be turned on or off by two separate switches. Table 1 shows how the hall light changes with various settings of Switch A and Switch B.

Table 1

Switch A Switch B Light

open open off

open closed on

closed open on

closed closed off

a. What logic gate would the information given in Table 1 represent? 1 mark

b. Sketch the symbol for the logic gate in part a. 1 mark

c. In the space below, draw a circuit in which Emma could use either of the two single-pole double-throw switches to turn the hall light on and off. 2 marks

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d. WriteaprogramordrawaflowchartthatusesthestateofSwitchAandSwitchBtorepresentturningthehalllightonandoff. 3marks

2018SYSENGEXAM 22

Question 8 (13marks)Emmahassomeappliancesthatoperateat240VAC.Shewantstooperatetheseappliancesusingelectricitygeneratedbysolarpanels.AsystemsdiagramisgiveninFigure6below.

solar panels batteries Block A AC appliance

Figure 6

a. WhyisFigure6anopen-loopsystem? 1mark

b. WhatisthenameofthesubsystemBlockA? 1mark

c. Writethepurposeofeachsubsysteminthetablebelow. 3marks

Subsystem Purpose

solarpanels

batteries

BlockA

d. Emmausesa240V,1kWvacuumcleanerfor30minutes.

Howmuchenergydoessheuse?Showyourworking. 2marks

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e. Thesolarpanelshaveanefficiencyof80%,thebatteriesare90%efficientandthecomponentsinBlockAare45%efficient.

Calculatethetotalefficiencyofthesystem.Showyourworking. 2marks

f. Emmaneedstoproduceanaverageof12kWhofenergyperday.

Ifthesunshinesforanaverageofsixhoursperdayandthereare10solarpanels,calculatethepowerratingofeachsolarpanelforanaverageday.Showyourworking. 2marks

g. Thebatterieshaveanominalvoltageof12Vandacapacityof250Ah.

Howmanyofthesebatteriesarerequiredtostore12kWhofenergy?Showyourworking. 2marks

2018SYSENGEXAM 24

END OF QUESTION AND ANSWER BOOK

Question 9 (5marks)Facialrecognitionisasoftwareapplicationthatiscapableofidentifyingorverifyingaperson’sidentityusingkeyfacialfeatures.Thetechnologyisusedinpassportsanddevicesecurity,amongotherthings.

Apartfromtheapplicationsmentionedabove,describeonepossibleapplicationoffacialrecognitionsystemsandthepossibleimplicationsofthisapplicationforsociety.

SYSTEMS ENGINEERING

Written examination

FORMULA SHEET

Instructions

Please remove from the centre of this book during reading time.This formula sheet is provided for your reference.

SYSENG EXAM 2

THIS pAGE IS bLANk

3 SYSENG EXAM

END OF FORMULA SHEET

Systems Engineering formulas

gear ratio final = gear ratio 1 × gear ratio 2 efficiency = output energyinput energy

× 100%

gear ratio = number of teeth on driven gearnumber of teeth on driver gear efficiencyTotal = efficiency1 × efficiency2

gear A rpmgear B rpm

number of teeth gear Bnumber of teeth

= gear A mechanical advantage load

effort=

pulley A rpmpulley B rpm

radius of pulley Bradius of pulle

=yy A force = pressure × area

voltage = current × resistance torque = force × distance

power = voltage × current frequency = 1period

area of circle = r2 ( = 3.14) speed = distancetime

circumference of circle = 2r

resistors in series Rt = R1 + R2 + R3 + … capacitors in series1

Ct 1 2 3+

resistors in parallel 1 1 1 1

2 3R R R Rt 1= + +

… capacitors in parallel Ct = C1 + C2 + C3 + …

two resistors in parallel R R RR Rt = +

Colour codes

Colour Value Colour Value

black 0 blue 6

brown 1 violet 7

red 2 grey 8

orange 3 white 9

yellow 4 gold 5%

green 5 silver 10%

2018 Systems Engineering Written examination · Reading time: 9.00 am to 9.15 am (15 minutes)...

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